Railway traffic controlling



9 Shee ts-Sheet l ,J. J. VAN HORN,

RAILWAY. TRAFFIC CONTROLLING APPARATUS Original Filed Sept 25, 1941 l RN I M WW 13 a N bkb N fis wm .fib w as QN u. v mm m r m E m @QE QN w-+| mV .w M%\ J A Q e m m B $1 L kmvmw wfiwww @mwfm @fig 7 6% w a -8 Ju N\ Y L g. um 5 Fm 2H lmmrm k 4 E w MN w W wwwfiwfimw m @N QE ERR Aug. 13, 1946.

w 3. v 6w .wwm Q5 v 5 H L whim J. J. VAN HORN RAILWAY TRAFFIC CONTROLLING APPARTUS Aug. 13, 1946.

- 9 Sheets-Sheet 2 Original Filed Sept. '25, 1941 w b v iii-- :1

INVENTOR 5 L6H Horn figm B E HLS' ATTORNEY J. J. VAN HORN RAILWAY TRAFFIC CONTROLLING APPARATUS Aug. 13, 1946.

pm vfiwwwwu M l A w E Egg ER L INVENTOR 9 Sheets-Sheet 3 Original Filed Sept. 25, 1941 7 [11s ATJI'ORNEY A g- 1946. J.J. VAN HORN RAILWAY TRAFFIC CONTROLLING AFPARATUS Original Filed Sept. 25, 194i w v N i i5 11 iii *QNQ ma i SQ ES 7 w INVENTOR Janzer' l izlzfh n.

HIS ATTORNEY g- 1946. r J. J. VAN HORN RAILWAY- TRAFFIC CONTROLLING APPARATUS Original Filed sept. 25. 1941 9 Sheets-Sheet 5 7 Aug. 13, 1946. ,J. J. VAN HORN' Re 2,7

RAILWAY TRAFFIC CONTROLLING APPARATUS Original Filed Sept. 25, 1941 9 Sheets-Sheet 6 M QUNU I INVENTOR J2me Van b51 12 H15 ALITORNEY Aug 13, 1946.

' J. J. VAN HORN RAILWAY TRAFFIC CONTROLLING APPARATUS Original Filed Sept. 25, 1941 9 Sheets-Sheet 7 SQUNU x mzHomz w TI 0\ w h I. n a T MHN u @T Tlflmm INVENTOR Jamar 4 HIS ATTORNEY J. J. VA N HORN RAILWAY TRAFFIC CONTROLLING APPAR ATIjS Aug. 13, 1946.

Original Filed se t. 25, 1941 I 9 Shets-Sheet B SQQMU INVENTOR Jamey 161111101 12.

HIS AfioRNEY Aug. 13, 1946. Y J. J. VAN- HORN Re 22,780 RAILWAY TRAFFIC CONTROLLING APPARATUS Original Filed Sept. 25, 1941 9 Sheets-Sheet 9 F\ i I 3 5 H i u HIS ATTORNEY .versal.

Reissued Aug. 13, 1946 RAILWAY TRAFFIC CONTROLLING APPARATUS James J. Van Horn, Pittsburgh, Pa., assignor to The Union Switch & Signal Company, Swissvale, Pa., a corporation of Pennsylvania Original No. 2,344,333, dated March 14, 1944,serial No. 412,279, September 25, 1941. Application for reissue January 25, 1945, Serial No.

53 Claims.

My invention relates to railway trafiic controlling apparatus and is directed more particularly to the control of traflic in a single track, two-direction system of signaling wherein centralized traffic control or other suitable manual control is used for establishing the traffic direction. A distinguishing feature of my system is that normally, no code is supplied to the single track stretch, the only current in the track being that due to the steady energy which I employ for maintaining the established traiiic direction and for other purposes. My system dispenses with all control line wires with the exception of the coded C. T. C. line circuit, if C. T. C. control is used, as will normally be the case, and with the exception of highway crossing control wherein I employ a line circuit to by-pass the steady energy and code around the highway crossing sections.

One object of myinvention is to provide a non-line-wire system of the above type which will be normally deenergized except for the steady energy which is used in the track circuits for block detection. Another object of my invention is to establish the desired traflic direction when proper to do so merely b moving a trafiic lever at a control office to a position corresponding with this direction, the checking and safety features of the system being brought into play automatically as a result of such movement. A further object of my invention is to provide certain intercontrols on the C. T. C. machine at the control office to prevent interference with the established traffic direction when the entrance signal is at proceed or the section is occupied by a train. A still further object of my invention is to provide a stick circuit for the traflic direction control relay at each end of the stretch, which is independent of the code equipment at the control ofiice, whereb a traflic reversal cannot be accomplished from the control office unless the conditions in the trackway are proper for such re- A still further object of my invention is to provide for the proper control of highway crossing signals and electric switch locks in a system of the character disclosed herein. A further object of my invention is to provide a continuous block indication for the single track stretch. Other objects, purposes, and characteristic features of my invention will be apparent from the description which follows:

I accomplish the foregoing objects by: normally transmitting steady or uncoded energy over the single track stretch in the established traffic direction to check unoccupancy of the stretch and to provide traffic locking whereby the absence of steady energy prevents a reversal of the traflic direction; removing the latter steady energy and transmitting coded current over the stretch from the new exit end to the new entrance end to provide block control for the entrance signal; reapplying steady energy behind the train to reset the track circuits to their normal condition; reclearing the entrance signal to' discontinue the steady energy so as to permit a following move; detecting the exit of a train by means of the steady energy receivedat the exit end following a train movement before a traffic reversal can be made; employing aback contact of the steady energy detecting relay (FSA) in the stick circuit forthe traffic direction control relay (FSR) so that the latter relay is independent of the control office and cannot be operated therefrom if steady energy is absent from the track stretch; employing only one pair of control line wires to provide 'a simple but eifective highway crossing application of the apparatus embodying my invention; employing frequency code of difierent code rates for providing a continuous block indication where the stretch includes one or more pairs of intermediate signals; employing back contact coding for eifectively relaying the steady energy and code at out sections; and providing a simple yet effective form of electric switch lock control without line wires.

The present invention is an improvement on the inventions disclosed in my copending United States application, Serial No. 410,504, filed on September 12,1941, and the copending United States application, Serial No. 411,481, filed on September 19, 1941, by Crawford E. Staples, both for Railway-traffic controlling apparatus.

I shall describe several forms of apparatus embodying my invention, and shall then point out the novel features thereon in claims.

In the accompanying drawings, Figs. 1a, 1b, 1c, and 1d taken together, with Fig. 1a at the left, are a diagrammatic view showing one embodiment of my invention as applied to a stretch of single track railway extending between the pass ing sidings PS! and PS2 at the two ends of the stretch, Fig. 1a being the control oifice for this stretch. Figs. 1e and if are diagrammatic views showing modified forms of the office equipment shown in Fig. 1a also embodying my invention. Fig. 1g is a diagrammatic view embodying my invention, showing a modification of a portion of the apparatus of Fig. 1c in which a polar directional stick relay replaces the two neutral directional stick relays of Fig. 10. Figs. 2a, 2b, and 2c, are diagrammatic views showing modified forms of the block indication apparatus of Fig. 1a, and also embodying my invention. Fig. 3a is a diagrammatic view showing the apparatus for electric switch lock control embodying my invention and represents the modification of the apparatus of Fig. 1 which would be required at an intermediate signal location. Fig. 3b is a diagrammatic view similar to Fig. 3a but adapted for a cut section location, and also embodying my invention. Fig. 4 is a diagrammatic view showing the adaptation of the apparatus for a highway crossing location, also embodying my invention. Fig. 5 is a diagrammatic view embodying my invention and showing a modification of a portion of the apparatus of Fig. 1c in which back contact coding apparatus replaces the front contact coding apparatus at the cut section of Fig. 10.

Similar reference characters refer to similar parts in each of the several views.

Referring first to Figs. ia-1d, inclusive, the stretch of track between the passing sidings PSI and PS2 is divided by means of the usual insulated rail joints at locations D, E, F, and G into a number of track circuit sections. Each of these track. sections is identified by the reference character T with a distinguishing prefix which also identifies the apparatus associated with that section. The signals which govern traflic movements through the single track stretch are the headblock signals 6 and'lil at the respective ends of the stretch and the intermediate signal 1 at location E. The cutsection location F could likewise be provided with a signal, if desired, by adding apparatus similar to that shown at location E.

Each section of the single track stretch is, in reality, provided with two track circuits, one eastbound and one westbound, each of which includes a code following track relay TR at one end and a source of track circuit energy, conveniently shown as a battery, at the other end. The track circuits could obviously be of the alternating current type and my invention contemplates such track circuits, the direct current type being shown only for purposes of simplicity. The track circuit current is properly coded under the influence of trafiic conditions, or as initiated by the operator at the central control ofiice shown diagrammatically in Fig. 1a.. Depending upon the direction of trafiic movement, only one or the other track circuit is time as will become clear hereinafter. The control relays involved in an eastbound move generally carry the prefix E or R (for right-hand) and those which control westbound moves include the prefix W or L (for left-hand) in order to make the disclosure more easy to follow.

For simplicity, I make use of but two-codes, these comprising direct current periodically interrupted at the rate of '75 times per minute for approach and 180 times per minute for clear signal indications. The coding is accomplished by means of suitable code transmitters 150T and I80CT which are well known. It is understood that for cab signaling purposes, alternating current coded over the contacts of these code transmitters could be superimposed on the direct current track circuits, but this added complication is unnecessary for an understanding of my invention. Following moves are provided for by means of directional stick relays and once traflic is established in a given direction, no further action on the part of the operator other than the intermediate signalefi'ective at any one clearing of the entrance signal is required for permitting entry of a following train.

The relays BW'F'SR and 8EFSR adjacent the two ends of the stretch are manually controlled traffic direction selecting relays which govern the direction of trafiic movement through the the stretch. The communication system by means of which the operator at the C. T. C. machine in the control oflice (Fig. 1a) may govern these relays may be of any suitable type, but preferably it is of the selective or code type in which communication is established intermittently by means of impulse codes transmitted over a single pair of line wires to the desired Control location or field station. The details of such a communication system do not enter actively into the present invention and it is deemed sufficient for an understanding of the present invention to point out that the traflic direction from right to left or westbound is established by moving the trafiic lever 8 (Fig. 1a) to the left-hand or L position so as to transmit a suitable code for energizing the traffic direction control relay BWFSR in the field station apparatus at the left-hand end of the stretch. It is understood that the communication system may also be used to govern the trailic leaving the single track stretch at either end by controlling the signals at such ends, and will also be used to provide an indication of trafiic and apparatus conditions within the stretch, as well as to prevent interference with or reversal of the established trafiic direction except under proper conditions, as will be pointed out hereinafter. One form of communication system suitable for use in my system is that shown in Letters Patent of the United States No. 2,229,249, granted to Lloyd V. Lewis on January 21, 1941, for Remot control system, and the general designation of the relays comprising the C. T. C. portion of my system, and the numbering of the terminal wires which are used to perform analogous functions, corresponds with that used in this patent.

I shall first describe the general features of operation of the apparatus embodying my invention and shall then describ the operation more in detail. It will be assumed, for simplicity, that the stretch does not include an intermediate signal and that the last =traffic movement Waswestbound so that lever B occupies its L position, causing the westbound trafiic relay BWF'SR to remain energized and the eastbound trailic relay BEFSR to be deenergized. With the westbound entrance signal IOL at stop, as shown, steady or uncoded energy flows from the east end (entrance end location G) over the intervening track sections to the west end (exit end, locationD) where it is used for the control of the unoccupied block indication light, shown in Fig. lo. I shall assume that it is desired to permit a westbound train to enter the stretch. When this indication is received at the control ofiice, a control code may be transmitted to pick up a home stick relay (IOLHSR) so as to initiate the operation of clearing the entrance signal 10L. When this control code is received and relay IOLHSR picks up, the steady energy is removed from the track circuit IOLT and from the remaining track circuits of the stretch, in succession. Removal of the steady energy is detected at the exit end and this permits code to be cascaded from the exit end D t the entrance end G to provide the block control for the intermediate and entrance signals, whereupon the entrance signal will be cleared and the westbound train may enter. As the train passes signal IGL, the block light at the control oflice will light up, to indicate the occupied condition. The coded energy will continue to be fed to the single track stretch after the train accepts the signal and enters the stretch, until after the stretch is vacated. It is understood, of course, that the coded energy will be cut off in the rear of the train in order to provide the usual following protection. When the train clears the stretch, coded energy will again be cascaded to the entrance end and will cause deenergization of the stick relay used for following moves,

whereupon steady energy will again be applied at the entrance end unless in the meantime a C. T. C, code has been transmitted to reclear the entrance signal.

In order to reverse the traffic direction from westbound to eastbound, steady energy must first be detected at the West end (location D) of the lock which permits deenergization of relay 8WFSR and energization of relay SEFSR following a reversal of lever B to the R position and the transmission of the necessary C. T. C. codes for this purpose. When the eastbound traffic direction is established, steady energy will again be present in the track sections of the stretch, as for the westbound trafiic direction but this steady energy will now be transmitted in the direction from west to east. Transmission of a C. T. C. code to clear the eastbound headblock signal ER will remove the steady energy and so will initiate the supply of coded energy from the east end (location G) to the new entrance end (location D) in the manner described above for permitting signal ER toclear sov that east-bound traffic may enter the stretch.

Having described the general features of operation, I shall next describe more in detail the sequence of operations occuring when traffic is established in a given direction, assumed to be westbound for purposes of explanation. The basic operation can be most easily understood by first connecting Figs. la and 1b directly with Fig. 1:1 to eliminate the complication. of the intermediate signal location and the out section apparatus.

With the entrance signals GR and lEL which govern moves into the single track stretch at stop, and with trafiic lever B in its L position for a westbound movement, the apparatus will be in the condition shown in the drawings wherein the westbound traffic direction control relay SWFSR will be energized and the opposing or eastbound traflic direction control relay HEFSR will be dee-nergized. At location G, relay HJLTCTM will be steadily energized over a circuit which includes the back point of contact 23 of relay TRWSR the function of which will be explained hereinafter, back contact 24 of the home stick relay HELHSR which controls signal L, back point of contact 25 of the eastbound traflic direction control relay (3 EFSR, back contact 26 of relay IELSR, which is the stick relay for signal IBL and picks up when the train passes this signal at any proceed indication, front contact 21 of the track repeater relay STM which is picked up whenthe short entrance section ST is unoccupied, and front contact 23 of relay IGLKM which checks the stop position of signal HJL and is picked up when. this signal is at stop. Steady energy from the direct current source IS is thus applied across the rails at the westbound entrance end over the front point of contact 29 and front contact .30 of relay IDL'IC'I'M which now remains constantly picked up. Accordingly, relay ERTR at the exit end is maintained steadily energized over the back point of contact 3| of relay BRTCTM which is deenergized at this time. Relays ERTM and BRTFSA will be continuously energized over the front contacts 32 and 33 of relays BRTR and BRTM, respectively. The circuit for relay SRTCTM will, of course, be open at the back contact 34 of relay GRTFSA. The presence of steady energy at the westbound exit end D provides the unoccupied block indication (Fig. 1a) and makes it possible for the operator to transmit a control code to clear the entrance signal IULA or IOLC.

When the operator transmits this signal-clearing code, he will energize the signal control relay IIlLHSR (Fig. 1d) through the code equipment at the field station (231) and will thus interrupt the steady energy circuit previously traced for relay IHLTCTM at back contact 24 of relay IHLHSR. The signal cannot, however, be cleared until code from the exit end is transmitted over the track and is received at the entrance end, as will appear more clear1y hereinafter. Steady energy will now be removed at the entrance end. Absence of steady energy at the exit end will result in the release of relays BRTR, GRTM, and BRTSFA at that end, whereupon a coding circuit for relay ERTCTM will be completed over the back contact 34 of relay SRTFSA, now closed. Relay GRTCTM will follow either or code, depending on whether the home relay iiLAHR for signal BL is deenergized or energized, respectively. As shown in the drawings, this relay is deenergized so that the 75 code circuit for relay GRTCTMdWll] include the back point of contact 35 of relay BLAI-IR, back contact 34 of relay GRTFSA (now closed), front point of contact 35 of relay BWFSR, back contact 3'! of relay ERSR. front contact 38 of relay 5TM, and front contact 39 of relay SRKM. Relay GRTCTM follows the '75 code and applies this code 3 to the exit end D over the front points of its contacts 3! and 40.

Looking again at the entrance location G, relay IQLTCTM at this location is deenergized so that the code following track relay l ULTR is continuously connected across the rails over the back point of contact 29 of that relay and so will follow the code supplied at the other end of the stretch. Relay I OLTM which is controlled over the front point of contact 4| of relay l DLTR and is of the code following type will likewise follow the code and will cause the energization of the front contact repeater relay IIJLTFSA over its front contact 42. The back contact repeater relay HJLTBSA will likewise be energized over the back point of contact 4| of relay IDLTR and the front contact 43 of relay IiiLTFSA. Relay IBLTBSA serves as an approach energizing relay for the decoding circuit of the decoding transformer DT which now becomes energized over the front contact 44 of relay IGLTBSA and the coding contact 45 of relay IiJLTM. Code detecting relay I BLCDR will now become energized from the output of the decoding transformer Over the rectifying contact 43 of relay lGLTM, in the usual manner. Since relay IOLCDR is energized, the circuit for clearing signal lllLA or lBLC may be completed in the usual and well-known manner.

When the train passes signal ISL, relay I OLI-ISR, (Fig. 1d) will become deenergized due to opening of front contact 41 of relay 9TM in its stick circuit so that if no additional'lever manipulation involving this stretch is made, '75 code will be applied to section GRT as soon as the train vacates this section, in order to permit following moves to be made. Relay IDLTR will again respond to this code and will energize relay IULCDR, as before, thus deenergizing the directional stick relay IOLSR at back contact 50 of relay IOLCDR. The westbound stick relay IOLSR. will have been picked up over the back contact 48 of relay 9TB and the front point of contact 49 of relay IOLAHR. The stick circuit for relay IOLSR includes back contact 50 of relay IDLCDR, back points of contacts and 49 of relays IDLCHAR and IOLAHR, and front contact 52 of relay IULSR. The release of relay IDLSR completes the pick-up circuit for relay IOLTCTM at back contact 26 whereupon this relay now becomes steadily energized over the circuit previously traced. The continuous energization of relay IOLTCTM causes steady energy to be applied to the westbound entrance and G, whereupon relay GRTR will become energized during off intervals of the code which is being supplied at the westbound exit end D. That is to say, the steady energy will feed through during the off intervals in the code. Energization of relay BR'I'R causes energization of relays BRTM and GRTFSA, as before, whereupon relay GRTCTM will become deenergized due to the opening of back contact 34 of relay BRTFSA, and will remain in this condition until signal IOL is recleared or until a traific reversal is initiated.

Summarizing the operation described thus far, the receipt of steady energy at the exit end permits initiation of the clearing operation for the entrance signal in which the steady energy is cut off at the entrance end and when this efiect reaches the exit end, coded energy is applied at that end and is detected at the entrance end. Presence of code at the entrance end permits completion of the clearing operation for the entrance signal.

A train entering the stretch provides for following moves by picking up a directional stick relay. When the trainvacates the stretch, code is reapplied at the exit end, releasing the directional stick relay which reapplies steady, energy at the entrance end. This steady energy feeds through the code and when detected at the exit end, cuts ofi the code at that end so that the apparatus is restored toits normal condition.

I shall now describe the manner in which a reversal oftraific direction from westbound to eastbound is accomplished, still assuming that no intermediate signals are present so that Figs. 1a, 1b, and 1d only are used.

With relay SRTR steadily energized due to the presence of westbound steady energy in the stretch, relay GRTFSA will be energized and code detecting relays BRCDR and BRDR will be deenergized. Since the last traflic movement was westbound, the traffic direction relay 8WFSR will be energized so that a circuit will be completed for energizing terminal 90 of the field station unit (234) (Fig. 1b). This circuit includes the back points of contacts 16 and 11 of relay BRDR and ERCDR, respectively, and the front points of contacts 18 and I9 of relays GR'I'FSA and BWFSR, respectively. Energization of terminal 90 of the field station unit results in the transmission of a C. T. C. code to the control ofilce in a manner which will be clear from the Lewis patent. This code will cause the westbound 8 block indicator relay BWTK to become energized. With this relay energized, the direction of 'trafilc may be reversed by a movement of the trafiic lever 8 to its right-hand position in which contact BB; is closed and contact 8W is opened. When this lever movement is made, a. circuit is completed to one winding of the polarized relay 8LPR over the front contact I09 which closes during the initial movement of the lever, front contact Hi8 of relay 8WTK and the lever contact 8E of lever 8. When polar contact III! of relay BLPR moves to its left-hand position corresponding to this energization, a control code will be transmitted to the field station unit (235, Fig. 1d) to energize the eastbound direction control relay BEFSR. The initial movement of lever 8 caused the starting relays 236ST and 234ST to become energized s that corresponding codes were transmitted to the field station units, as is well known in C. T. C. practice as exemplified in the Lewis patent. The code resulting from energization of the starting relay 236ST caused the pick-up of the eastbound direction control relay BEFSR, as just described. The code transmitted by virtue of the energization of the starting relay 234ST caused the release of the westbound direction contral relay BWFSR. Relay SWFSR will release due to the interruption of the circuit to terminal I02 which extends through contact I15 of relay 2341s, at the polar contact H0 of relay BLPR, now reversed so that contact I It) occupies its left-hand position.

It will be observed that if relay BEFSR becomes energized before relay BWFSR is released (which may happen due to the fact that codes must necessarily be transmitted to the diiferent field station units in succession) the energization of relay BEFSR will cause relay IQLTCTM to respond to code instead of steady energy. Accordingly, coded energy will be applied instead of steady energy at the new entrance end (location G) and the code will be detected by relays ER'IR, BRTM, BRTFSA, and GRTBSA, at location D. Since relay BRTFSA is thus continued in its energized position, no change in the traflic set-up at location D will ccur until relay BWFSR is subsequently deenergized. When this occurs, relay ERTCTM will be continuously energized over the circuit which includes the back point of contact 2H] of relay 'IRWSR, back contact of relay GRHSR, back contacts 36 and 31 of relays BWF'SR and BRSR, respectively, and front contacts 38 and 39 of relays 5TM and GRKM, respectively. Since relay BRTCTM is now steadily enexit end.

During the off interval of the code to which relay IOLTCTM is responding, relay IULTR will be connected across the track and will respond to the steady energy, energizing relays IDLTM and I ULTFSA, in sequence, The energization of. relay IOLTFSA will deenergize relay IBLTCTM at its back contact 55 so that coded energy will be removed from the east end (G) of the stretch.

Steady energy will continue to be supplied at the west end (D) until signal GR is cleared for the eastbound move, whereupon steady energy will be 9 removed because of the energization of relay BRI-ISR which has a back contact 55 included in the steady energy supply circuit for relay BRTC'IM.

If relay BWFSR becomes deenergized before relay GEFSR, picks up, then relay BRTC'IM will be energized on steady energ and will impress steady energy on the track at location D. This steady energy will oppose the steady energy impressed on the track by relay IBLTCTM at location G, but this will have no adverse effect. As soon as relay 8EFSR picks up, relay IOLTCTM will have its energization changed from steady to coded, thus permitting relay IOLTR to become energized n the first off interval of the code, with the consequent energization of relays IGLTM and IBL'IFSA. Pick-up of relay IBLTFSA will deenergize relay IOLTCTM and so will discontinue the supply of coded energy to the track. The track will now have steady energy alone flowing in the rails from the new entrance end D to the new exit end G. From this point on, the establishment of the eastbound trafiic direction will be clear from the analogous description already presented for the westbound trafiic direction.

Having described the basic operation employing Figs. la, 11) and 1d, I shall now describe the operation taking plac when the single track stretch includes an intermediate signal location and a cut section location. For this purpose, Fig. 1c is inserted between Figs. 1b and 1d of the drawings. To avoid unnecessary duplication, the present description will be confined as much as possible to the apparatus of Fig. 10.

With traffic assumed to be established in the westbound direction, as before, and the stretch unoccupied, steady energy is fed in the direction of traffic from location G to location D. When this steady energy is received at location F, relay lAETR will be energized over the back point of contact 51 of relay 1AECTM and will energize relay TAWCTM over its front contact 58. Relay 1AWCTM will apply steady energy from the track battery IS to section 1RT over the front point of its contact 59 and front contact I16. At the intermediate signal location E, the steady energy will energize relay 1ETR as well as relays IETFSA and 'IWCTM. All other relays at this location (except the code transmitters) will be deenergized. The circuit for relay 1WCTM includes the front point of contact 6!] of relay 1ETFSA, the back points of contacts 6| and 62 of relays 1E8 and 1HR, respectively, and the back contacts 63 of relay 'IWS. Steady energy is repeated into the section GRT over the front point of contact I11 and the front contact 64 of relay 1WCTM. Accordingly, the manner in which steady energy can be readily transmitted around a cut section location as well as an intermediate signal location in the system embodying my invention will be readily apparent.

I shall next describe how a control is established for clearing the entrance signal IL for a westbound move. Energization of the stick relay lllLl-ISR to clear one of the IllL signals removes the steady energy from the westbound entrance end at location G and causes the deenergization of relays 1ETR, lETFSA and 1WCTM at the intermediate signal location E. Steady energy will consequently be removed from section GRT so that relay GRTR will also release. The absence of steady energy at location D will cause coded energy to be applied to section GRT, due to the release of relay GRTFSA, as explained hereinbefore. This coded energy will be detected by the code following operation of relay 1WTR and by the energization of relays 1WTFSA, 1TM, 1BSA, 1HR and 'IWS, if the code is '75. Relay 'IWTFSA will remain steadily picked up, as will relays 1BSA, 1HR, and 'IWS. Relay 1'I'M is a code following relay which is now energized over the back point of codin contact I18 of relay 1WTR and the front point of contact I19 of relay l'WTFSA. The code operation of relay lTMwill accordingly energize the code detecting relay 'EHR over the rectifying contact l 80. The circuit for relay 1W8 include front contact 10 of relay 1H3, back point of contact 1| of relay 'IETFSA, and the front point of contact 12 of relay 'rWTFSA. If the code supplied to section BRT is 180, the 180 code detecting relay 1DR will also be energized so that signal 1W will then display either an approach or a clear indication, depending on the code.

Relay 1ECTM will now follow 180 code and will apply energy of this code frequency to the section 1RT and when the 180 code is detected at location G, signal IBL will be permitted to display a clear indication. The circuit for relay 1ECTM under this condition will include the back point of contact of relay TETFSA, wires and 66, contact 61 of coder ISGCT, front point of contact 68 of relay 1BR, and back contact 59 of the opposing directional stick relay 1E8. Now, when the train passes signal 1W, shunting out relay 'IWRT, all of the relays 'IWTFSA, 1TM, TBSA, 1HR and 1DR will become deenergized. The westbound directional stick relay 1W8 is slow in releasing and so will establish an obvious stick circuit for itself over the back point of contact 13 of relay 1WTFSA and its own front contact 14. Relay 1ECTM will now follow '15 code, its coding circuit including the back point of contact 60 of relay 1ETFSA, wire I 8|, code contact 15 of the coder 15CT, front point of contact 16 of relay 1WS, back point of contact 68 of relay 1BR, and back contact 69 of relay 1ES. Accordingly, code is applied by relay 1ECTM to the section 1RT, although this code is as yet ineffective in this section due to occupancy by the train.

When the train Vacates section 1RT, the '75 code will cause operation of relay IOLTR at location G so that the code detecting relay IOLCDR will be energized. Energization of this relay will open the circuit of the stick relay IDLSR (which became energized when the train passed signal IflL) to provide a control for permitting a following move to be made into the occupied stretch. Deenergization of relay IDLSR will permit the energization of relay IDLTCTM on steady energy over the previously traced circuit, provided one of the [EL signals is not to be re-cleared. The steady energy applied at location G will feed through the code to location E and will be detected during the off intervals of the code by relays 1ETR and 1ETF'SA at the intermediate signal location. The energization of relay 1ETFSA opens the coding circuit for relay 1ES'I'M which was just traced, at the back point of contact 60, thus removing coded energy from section 1RT.

It will be noted that the steady energy which is applied at location G cannot be relayed to the other end D of the stretch until coded energy has been received from such other end to deenergize the westbound directional stick relay 1WS which has a back contact 63 in the energizing circuit for relay 'IWC'IM. The deenergization of relay 'IWS will take place when the train clears the sections ERT and 5T between signals 1W and GR, whereupon coded track ene gy will be applied at loca- IWTR and 1WTFSA, thus interrupting the stick circuit for relay 'EWS at the back point of contact I3 of relay TWTFSA. When relay 'IWS close its back contact 63, relay 'IWCTM will become steadily energized over a circuit which includes the front point of contact 60 of relay IETFSA, back points of contacts BI and 62 of relays IE8 and IHR, respectively, and the back contact 63 of relay 'IWS.

During the time that a westbound train is between the signals IW and GR, a following move may be made by reenergizing relay IOLI-ISR at location G through the C. T. C. system, thus removing the steady energy from the track sections between signals IE and IllR. Now, with relay 'IWS energized, relay I'ECTM will follow '75 code and will apply this code to sections IRT and IOLT. The energizing circuit for relay 'lECTM will be the same as previously traced in connection with the passage of a westbound train beyond signal 'IW. The detection of the 75 code at location G will permit one of the IOL signals to display an approach indication for the following train, as will be obvious.

I shall next describe the operations involved in a reversal of traffic when the stretch includes an intermediate signal location. In connection with this reversal of the traflic direction from westbound to eastbound, reference will be had to r the apparatus at the control oflice or C. T. C. machine shown in Fig. la. To accomplish the reversal of the traffic direction to eastbound, steady energy must be flowing in the westbound direction from location G to location D in order that the front point of contact I8 of relay ERTFSA in the energizing circuit for terminal 50 of the field station unit of Fig. lb may .be closed so that this terminal will be energized under the assumed condition. Accordingly, a code will be sent out from this field station to the control oflice of Fig. la so that relay SWTK on the C. T. C. machine will be energized in order to permit a reversal of the polarized relay BLPR which is controlled by the traffic lever B. As previously pointed out, the steady energy will follow a train as it passes over the stretch, progressively energizing the track circuits and associated apparatus until when the train completely vacate the stretch, all of the track circuits will be reset on steady energy which is thenormal condition of the system. The energizing circuit for terminal 90 of the field station unit also includes the back points of contacts IE and I! of code detecting relay SRDR and BRCDR (both deenergized since code is absent from section GRT) and the front point of contact I9 of 1 the westbound trafiic direction control relay 8WFSR,in addition to the front point of contact 18 of relay ERTFSA, mentioned above. Relay SWFSR is still energized since the last traffic movement was westbound.

The preliminary movement of the trafiic lever 8 results in the pick-up of both starting relays 234ST and. 236ST which control the transmission of C. T. C. codes to the field stations 234 and 236 at locations D and G, respectively. The code transmission circuit for energizing the respective trafiic direction control relay for the new direction will, however, not be completed until a reversal of the polar stick relay BLPR which remains in its last energized position, is obtained. Under the condition assumed, relay 8LPR will receive reverse energization over the lever contact 8E (now closed), front contact I08 of relay B WTK, and lever contact I09 (lever contact I08 having become closed during the preliminary movement of the lever 8). At this point it is advantageous to call attention to the trafiic locking functions performed by the apparatus embodying my invention, with special reference to the apparatusof Fig. 1a. As will now be apparent, the westbound block indication relay BW'I'K (or terminal 90 of the field station unit) cannot be energized unless the stretch is unoccupied and the westbound signal IOL is at stop so that westbound steady energy flows over the stretch. The energization of relay BWTK closes front contact I82, and since polar contact IIO of relay 8LPR is in its right-hand position, the westbound traflic relay BW'FK is energized over an obvious circuit, closing a circuit over its front contact I20 for the westbound traflic direction light 8WFKE. If new a C. T. C. code is transmitted by the operator to location G for initiating the clearing of signal IOL, the steady energy will be removed from the stretch for reasons hereinbefore pointed out. The same will be true if the stretch is occupied, or the westbound steady energy is removed for any other reason. As a consequence, relay GRTFSA will release, deenergizing terminal 90 and causing relay 8WTK to release. Accordingly, it is now no longer possible to reverse relay 8LPR even if the traffic lever itself is reversed to close contact 8E, because the reverse energization for relay BLPR is interrupted at front contact I08 of relay 8WTK. It will be clear, therefore, that polar contact H0 is now locked in the right-hand position corresponding with westbound traffic so that no traffic reversal can be accomplished unless westbound steady energy is restored over the stretch. The westbound trafiic relay 8WFK will, in the meantime have its stick circuit closed over polar contact IIO to the right, wire I83, and its own front contact I84 so as to maintain the westbound traflic direction indication during the time that signal IOL i clear or the stretch is occupied by a westbound train. It will be apparent, therefore, that the apparatus embodying my invention provides a, highly eifective, yet relatively simple form of traffic locking which prevents interference tained, contact I I0-of relay 8LPR is now closed in the reverse or left-hand position and since relay 2368 is now energized, energy is supplied to terminal I04 of the office unit which terminal corresponds with the similarly numbered terminal of the Lewis patent. The circuit for terminal I04 includes polar contact H0 in its left-hand position, wire I85, and front contact I85 of relay 2365, now closed. Energization of terminal I04 results in the transmission of a code which causes pick-up of the eastbound traflic direction control relay BEFSR at the field station 235 at loccation G. When relay BEFSR picks up following the movement of lever B to its R position, the

' steady energy previously supplied at location G I circuit operations. The steady energy which was previously applied at location G when the trafiic direction was westbound caused relays TETR, 'IETFSA and lWCTM to be steadily energized. When the change to code supplied at location G occurs, relays TTM, 'IBSA, IHR, and IE will also become energized. Relay 'IWCTM will now operate on code, its circuit including the back point of contact 73 of relay 'EWTFSA, wire Ill, contact H2 of code transmitter HHICT, front point of contact 62 of relay 'IHR, and the back contact 63 of relay TWS. The code operation of relay l'WCTM will cause code to be supplied to section GRT beyond the intermediate signal 1W.

Considering now the other end of the stretch at location D where steady energy is now being applied because of the release of relay BWFSR, the application of this steady energy will also be detected at the intermediate signal location. E by the steady energization of relays JWTR. and 'IWTFSA since the steady energy will feed through the code during the off intervals, as previously pointed out. Pick-up of the latter relay opens the circuit for relay 'IWC'IM, thus removing code from section BRT. The pick-up of relay TWTF'SA also opens the circuits of relays IES, 'iTM, TBSA, and THE, whereupon relay TECTM will become steadily energized and will relay the steady energy from section BRT into sections 'iRT and liiL'I'. The steady energy circuit for relay TEC'IM includes the front point of contact 13 of relay 'IWTFSA, back points of contacts iii and 68 of relays 'IWS and 'lHR, respectively, and back contact 69 of relay IES. The steady energization of relay IEICTM results in the obvious deenergization of relays 'IETR and TEETFSA. Accordingly, the stretch has now been reset on eastbound steady energy so that the operator may initiate clearing of the eastbound signal 6R to permit an eastbound train to enter the stretch.

The operation of the apparatus at the intermediate signal location when an easbound train moves over the stretch is similar to the previously described operation for a westbound train movement, so that this description. need not be re-' peated. Also, the operation of the apparatus at the out section location will be clear from the previous description without added explanation.

I shall next describe the block indication features of my invention, considering first that the stretch has no intermediate signals, as will be the case when Figs. 1a., 1b, and 1d are placed end to end. Figs. 1b and 1d of the drawings, when Fig. covering the intermediate signal location is inserted therebetween, show the block indication apparatus for a stretch of track having one intermediate signal and this indication apparatus has already been described. Figs. 2a and 212 show the modifications required in the control for the track indication relays 8WTK and BETK, respectively, when no intermediate signals are involved as is the case when Fig. 1c is removed from the stretch. Referring to Fig. 2, with steady energy in the track being supplied at location G and feeding westbound, as will be the case for westbound trafiic, a circuit for causing energization of the westbound track indication relay BWTK located at the control ofiice will be completed over the back point of contact N3 of relay GRCDR and the front points of contacts 1 l4 and H5 of relays BRTFSA and BWFSR, respectively, to terminal 90 of the field station unit. As pointed out hereinbefore, energization of terminal 98 causes the transmission of a code from the field station to the control ofiice to cause energization of relay 8WTK. Relay BETK (Fig. 2b) responsive to code from the opposite end of the stretch is, of course, deenergized at this time. Accordingly, the circuit for the block light which includes back contacts H8 and Ill of relays BWTK and GETK, respectively, is incomplete so that the block light is dark and the indication is unoccupied block.

When code is applied at location D and transmitted over the stretch for a westbound move, a circuit wil1.be eirective for energizing terminal 9!] of the field station unit 236 at location G over the front point of contact H8 of code detecting relay IULCDR (now energized) to cause the energization of relay BE'IK at the control office through the transmission of a suitable C. T. C. code. Relay BWTK will at this time be deenergized because of the deenergization of terminal Q0 of the field station unit 2334 resulting from the removal of steady energy from the track. Accordingly, the circuit for the block light will again be incomplete so that the indication is unoccupied block. If a westbound train should now enter the block, relay HILCDR will be deenergized and so will complete a circuit over the back point of its contact HE and the back point of contact H9 of relay lfiLTFSA (now also deenergized) so as to energize terminal 94 of the field station unit which results in the transmission of a C. T. C. code to deenergize relay SETK at the office. With relays BW'IK and SETK both released, the circuit for the block light will be completed at back contacts H6 and ill so that the block light will now indicate occupancy of the single track stretch.

Considering next the traffic indication, it is unimportant as to which of the two traffic directional control relays (SWFSR or tEFSR) is operated first when the trafiic direction is changed from westbound to eastbound, as the final circuit condition will be such that relays ESRCDR, BRTFSA, and 8WFS-R will all be deenergized so that a circuit will be completed for energizing terminal 94 of the field station unit 234 so as to cause deenergization of relay 8WTK at the office. On the other hand, relays EEBLTFSA and 8EFSR will be energized so that a circuit will be completed for energizing the terminal 99 of the field station unit 236 so as to energize relay EETK. The time required to complete these relay ope-rations and the order in which the indication codes are transmitted may produce a condition such that the block light may be illumi nated for a short interval of time even though the block is the-n unoccupied. This type of indication will ordinarily not persist for more than a very few seconds unless the indication codes are delayed by control codes which receive preference in transmission.

The reversal of the polar contact Hi! of relay BLPR when the traffic direction was changed from Westbound to eastbound opened the circuit for the westbound traffic relay BWFK whereupon the opening of front contact I293 of this relay caused the westbound traffic indication light 8WFKE to become extinguished.

The energization of relay SETK with the polar contact H0 of relay 8LPR. closed to the left (for eastbound trafiic) completes the circuit for the eastbound traffic indication. relay SEFK over its front contact Hi. The latter relay, in turn, closes its front contact I22 toilluminate the eastbound traffic direction light SEFKE. Relay EEFK is provided with a stick circuit over its own front contact I23 and wire I so that it will remain energized as long as relay BLPR has its contact III! closed to the left for the eastbound traific direction. This provision is expedient since relay BE'IK will become deenergized when a control is transmitted to clear the 6R. signals and eastbound steady energy is discontinued.

Where the stretch includes one pair of intermediate signals the block indication will be provided by the apparatus shown in Figs. 1b and id, as previously pointed out. This apparatus is the same as that shown in Figs. 2a and 2b and described above, with the exception that since one pair of intermediate signals is present within the stretch, the 180 code decoding relays (BRDR and IOLDR) at the two ends of the stretch are used in the circuits for energizing the terminal 50 of the respective field station unit, to pick up the track indication relay, and in the circuits for energizing terminal 94 which causes a release of this relay. The circuit change occasioned by the addition of relays BRDR. and IKILDR will, accordingly, be clear from the drawings without added description. As before, relays BWTK and 8ETK will detect the unoccupied condition of 'the stretch when steady energy is present IIILDR of Figs. 1b and 1d, respectively. In all, other respects, the control circuits for relays,

BWTK and BETK will remain as in Figs. 1b and. 1d.

Referring to Fig. lo, the apparatus shown in this figure is similar to that shown in Fig. 10 with the exception that instead of using two neutral directional stick relays WS and ES, one for each direction, I employ a single directional stick relay DS. This relay is of the polar stick type and operates its polar contact I10 to the left when energized with current of one polarity over a circuit which includes the back point of contact I'll of relay WTFSA, front contact I12 of relay HR, and the front point of contact I13 of relay ETFSA, When the traffic direction is reversed, relay D8 will open contact I10 and will close its polar contact I14 to the right by virtue of an energizing circuit which includes the back point of contact I13 of relay ETFSA, front contact I12 of relay HR, and front point of contact I1I of relay WTFSA. Polar contacts I10 and I14 control the application of code for a westbound or an eastbound following train movement, respectively, in a manner which will'be clear from the previous description.

Referring next to Fig. 3a, this figure shows the apparatus embodying my invention applied to the control of an electric switch look within the single track stretch, the lock being associated with an intermediate signal. The various relays in this figure carry similar designations to those used for the relays in Figs. lb, 10, and 1d, and these relays perform broadly the same functions so that it will be necessary to describe only those features wherein the apparatus of the present figure differs from that of Fig. 1. It will be under-, stood. of course, that Fig. 30. can be substituted, for example, for Fig. 10, or inserted between Fig. 1c and either Fig. lb or 1d to provide a complete,

In the system embodying my invention, a train 7 on the main track may secure an unlock automatically and enter the siding without any additional action being required on the part of the operator at the control oflice. In this case, the unlock is obtained when the train occupies the short releasing track section OT which may be of the order of 100 or 150 feet in length. The circuit for energizing the switch lock 13W includes the back contact I21 of the track relay OTR for the section OT and the reverse contact I28 (now open) of the manually operable lever 1A which the trainman operates before an unlock is obtained. The trainmen will reverse both levers 1A and 1B, allowing a train to enter the siding, whereupon both of these levers should be restored to the normal position, as shown, unless the train is to leave before the arrival of another train. The purpose served by lever 1A will be explained in connection with the operation involved in obtaining an unlock to permit a train to leave the siding. This operation will now be described.

In order to render the switch lock operation more readily understandable, I shall assume that Fig. 3a. has been substituted for Fig. 1c in the system of Fig. 1 and shall first point out briefly the main steps taking place during the operation of obtaining an unlock. The action of throwing the bolt lock lever 1A cuts 01f the steady energy (assumed flowing westbound) at the track switch location, resulting in current of 75 code feeding back from the west end to the switch location, and also lighting the block light on the operators control panel. Obviously, unless steady, energy is present at the track switch location, throwing the bolt lock lever TA will have no effect.

The illumination of the block light indicates to the operator that the bolt lock has been thrown, and that he may reverse the switch lock lever 1 at the control ofiice. This operation transmits a C. T. C. code to locationG (the field station where the steady energy originates) for the purpose of cutting off the steady energy at that location and applying 75 code. When code is received from both directions at the switch 10- cation, the electric lock becomes energized so that the track switch may now be reversed.

I shall now describe the operation more in detail. As pointed out above, in order to secure an unlock for a train on the siding, the trainman will first operate lever 1A. It is assumed that traffic has been established in the westbound direction and that steady energy is being fed in the westbound direction from one end of the stretch through the switch lock location to the other end.v Traific should ordinarily be set in the direction of train movement in order to provide intermediate signal control. However, the system will operate satisfactorily with trafiic established in either direction. The reversal of lever 1A under the assumed condition results in the deenergization of relay OTWM through the opening of contact I29 of lever 1A (which is closed only in the normal position of lever 1A), as will be obvious from the drawings. Relay OTWM, in releasing, opens the circuit for relay WCTM so that the steady energy is cut on? from section WT and any other sections west of the interme- 17 diate signal location. Coded energy will then be applied to the track at the west end of the block (location D of Fig. 1b) in the usual manner and this energy will be detected by relay WHR adjacent the switch lock location. This coded energy will, however, not be relayed eastward, because relay ECTM also has its energizing circuit open at the front contact I of relay OTWM. The latter relay has been provided with a stick circuit to insure that it will not be deenergized should lever'lA be reversed during a time when coded energy is efiective in the track circuits and an entrance signal is clear, or a train is approaching the look. In either case, it would be undesirable to interrupt the coded track circuit energy with the possibility of interfering with the train movement. The normal pick-up circuit for relay OTWM includes the armature contact- I3! of lock 'IBW, the normal contacts I32 and I29 of levers 1B and IA, respectively, front contact I33 of relay OTR, winding of relay OTWM, front contact I34 of relay OTR, and normal contact I35 of lever 1B. The stick circuit for relay O I'WM includes armature contact I3I, normal contact I32 of lever 1B, wires I36 and I37, front contacts I38 and I39 in multiple of relaysEHR and WHR, respectively, wire I40, front contact I4I of relay O'I'WM, and wire I42. It will be apparent that front contact I4-I in this circuit bypasses the normal contact I29 of lever IA. Contacts I32 and I35 of lever 1B can be the. usual switch circuit controller contacts and need not require a separate lever. such as 'IB.

After the trainman has operated lever IA under the proper conditions, the operator at the control ofiice will send a control code to both ends of the stretch with the switch lever I in the control office in its unlocked (R) position. Accordingly, the switch control relay IRWSR (Fig. 1d) at the entrance end of the block corresponding with the established trafiic direction (westbound) will become energized snoe the eastbound traflic directioncontrol relay SEFSR is now deenergized and has its back contact I43 closed. Relay IRWSR at the other end of the block (location D) will not become energized because the westbound trafiic direction control relay BWFS-R is energized under the assumed condition of Westbound traffic and has its back contact I88 open.

The control circuit fonrelay 'IRWSR includes, in addition to the back contact I43 of relay SEFSR, the front contact I44 of relay IDLKM, back contact I45 of relay IOLSR, and back contact I45 of the time element release ITER. Front contact I44 of relay II'ILKM checks that the entrance signals are at stop. Back contact I45 of the directional stick relay IIILSR prevents the energization of relay 'IRWSR if relay IDLSR is energized. This provision makes it possible for coded energy to be received after the train passes the first intermediate signal to deenergize relay IIlLSR, after which steady energy would normally be applied to the track. circuit and transmitted in the westbound direction. Back con.- tact I46 of the time element release. 'ITER checks that this relay is in its fully released position so that a full time interval will be measured by the relay, when energized. Relays 'ITER and 'ITESR are required only when switch locks are located at automatic signals (as in Fig. 3a), and in this I case only at the east end of the block. Thus, these timing relays are only required at the east end of the block when it is possible for a train leaving a'siding equipped with anelectric switch lock to pass an intermediate signal and then move past an intermediate signalinthe opposite direction, The end of the block toward which such a train movement could be made is the one which would require the timing relays ,TER and TESR. r

The energization of relay lRWSR at location G changes the control circuit of relay I-BLTCTM from stead energy to code. This control circuit now includes the '75 code terminal, back point of contact I4! of rela IHRAHR, back contact 56 of relay IBLTFSA, wire I89, front point of contact 23 of relay 'IRWSR, back contact 24 of-relay EGLHSR, back point of contact 35 of relay SEFSR, back contact 25 of relay IIl LSR, and front contacts 21 and 28 of relays STM and IQLKM. Relay IOLTCTM will now apply coded energy to the track. at location G and this energy will be fed in the westbound directiontoward the-switch lock. location. When this code is clet'ecteclat the switch lock. location by virtue of the energization of relay EHR, the switch lock circuit will become completed over a path which includes the front point of contact I48 of relay'WHR, wire I49,

front contact I50 of relay EHR, wires I5I and I52, and reverse contact I28 of lever IA.

It will be noted that in the case of theintermediate signa1 type of switch lock location, as shown in Fig. 3a, the circuit for the electric switch lock 'IBW includes-front contacts I53 and I54 of the eastbound and westbound directional stick relays ES and WS, in multiple with front contacts 50 and I48, respectively, of relays EHR and WI-IR. Accordingly, with this arrangement, an unlock could be obtained: at lock 'IBW following the movement of a westbound train past the intermediate signal W.

After the unlock has been obtained. and the switch has been reversed, the unlock control may be cancelled by transmitting a C. T. C. code, with lever I. in the normal position, to deenergize relay lRWSR. at location G, thus completing a circuit for the thermal time element relay 'ITER over the back contact I55 of relay 'IRWSR and the back point of contact I56 of relay ITESR which became deenergized when relay 'IRWSR was energized. After the expiration of the required time interval, the front contact I51. of relay 'lTER will close and. will complete an obvious energizing circuit for relay 'I'IESEL Pick-up of relay TESR. will open the circuit for relay 'ITER at. the back point of contact I56, thus permitting the thermal rela to cool and to reclose its check'- ing contact M3 in the previously traced circuit for relay 'IRWSR. Relay 'ITESR will remain energized until such time as relay 'IRWSR is re-. energized for another unlock of the electric switch lock. x

If the train leaving thesiding were to move in the eastbound direction while a westbound train occupied, the block west of the switch lock, the operator at the control office would leave lever I in the reverse position so as to feed coded track circuit energ toward the train, as mentioned hereinbefore, in. order that the intermediate signals may display proceed aspects. If the block were unoccupied, the operator would have established the eastbound direction of traffic so that the train could proceed east in theusual manner and lever I could be restored to itsnormal position at any time after the switch became unlocked.

In view of the explanation which has been presented above in connectio with the apparatus of Fig. So. for obtaining an unlock of a switch lock at an intermediate signal location, it-is believed that the operation of the apparatus of Fig. 3b will be entirely clear from the drawings. This figure shows the switch lock 1BW positioned at a cut section location so that a considerable portion of the apparatus of Fig. 3a can be dispensed with in Fig. 3b. All of the steps involved in the switch-lock operation are the same in both cases, so that a detailed description of the operation is unnecessary. The chief difference resides, of course, in the absence of the directional stick relays ES and WS; the repeating relays ETM and WTM; and the decoding apparatus which provides selective control of the intermediate signal indications. Relay OTWM is again provided with a, stick circuit which prevents release of this relay by a reversal of lever IA at a time when coded energy flows in either direction over the stretch. The code detection in Fig. 3b is accomplished by relays ETBSA and WTBSA which will not be energized unless the respective track relay ETR or WTR is following code. When code is present, the stick circuit of relay OTWM will accordingly include one or the other front contacts I90 or I9I of relays ETBSA and WTBSA. respectively, instead of the corresponding contacts I38 or I39 of relays EHR and WHR, re-

spectively, in Fig. 3a. The normal pick-up circuit for relay OTWM is the same inboth figures.

It is apparent, therefore, that the apparatus lends itself readily to the control of switch locks either at an intermediate signal location or at a cut section location.

In either of the foregoing arrangements, the switch lock lever "I, in the control ofiice may be restored to its normal position at an time after the track switch has been reversed. This is possible because the track switch does not have to be unlocked in order to be thrown to normal. An unlock of the switch can also be obtained (fol lowing a reversal of lever 'IA) if the short detector section OT immediately in advance of the switch is shunted, releasing relay OTR, which closes an auxiliary pick-up circuit for lock IBW over its back contact I21, wire I52, and reverse contact I28 of lever 1A. This provision makes it possible for a train occupying the main single track stretch to enter a siding at any time.

Referring next to the highway crossing modiflcation shown in Fig. 4, I employ neutral direct current track circuits for the approach control of the highway crossing operating circuits and for the short track circuit through the crossing. The operation of the highway crossing stick relays WSR and ESR and of the highway crossing signals will be effected in the usual and well-.

known manner. It will be understood, also, that ngs showing the highway 11 of my invention may be my two sheets of the system shown in Fig. 1 of the drawings, such as between Figs. 1b and 10, .Figs. 1c and 1d, or between any of these figures and Fig. 3a or Fig. 3b when the stretch includes a track switch location. As will be apparent from the drawing of Fig. 4, the steady energy and track code of my system are carried around the approach sections'at the highway crossing location over line wires which include front contacts of the track relays for these sections.

The operation is as follows, assuming that Fig. 4 is inserted between Figs. lb and 101. When steady energy is being received from location G of Fig. 1d and transmitted westbound, the code following track relay ETR will be continuously energized, as will also the code transmitting re- 2o lay WCTM. The circuit for relay WCTM passes over the line wires and includes the front points of contacts I58 and I59 of relay EC'I'M, front contacts I60 and I6l of track relay AETR, front contacts I62 and I63 of track .relay O'I'R, back contacts I64 and I 65 of the stick relays ERS and WSR, respectively, front contacts I66 and I61 of track relay AWTR, and the back points of contacts I68 and I69 of relay WTR. The energization of relay WCTM applies steady energy to the track circuit WT west of the crossing location in the usual manner. When steady energy is removed at location G, as it will be when the westbound entrance signal is cleared, relay WCTM (and relay ETR) will become deenergized, thus permitting the code following track relay WTR to respond to code which is now being transmitted eastward from location D, since the trailic direction is assumed to be westbound.

The code operation of relay WTR will now cause relay ECTM to follow code and to repeat this code into the track section ET east of the'crossing. The coding circuit for relay ECTM includes the front points of coding contacts I68 and I69 of relay WTR, the line circuit previously traced for relay WCTM, and the back points of contacts I 59 and I59 of relay ETR. It will be apparent, therefore, that the presence of the highway crossing location within the single track stretch does not interfere in any manner with the transmission of either the steady energy or the coded energy whichare used in establishing traffic in one or the other direction through the stretch. Also, there is no interference with the restoration of the system to its normal condition following the passage of a train over the stretch.

It will be noted that the line circuit in Fig. 4 is so controlled by the eastbound and westbound track relays that the two line wires transmit I. steady energy in one or the other direction according as the eastbound or the westbound track relay is steadily energized, and the same two line wires transmit code in the other or the one direction according as the westbound or the eastbound track relay, respectively, is following code. The positive and negative source terminals (B and C, respectively) at the two ends of the line circuit are connected in reverse order, so that when relay WTR is energized, the upper wire I93 has the positive energ terminal B connected thereto, whereas when relay ETR is energized, this wire is connected with the negative energy terminal C. The same is true for the lower wire I94 to which relay ETR connects positive energy and relay WTR connects negative energy. Since the operation of the system is such that relays WTR and ETR are never up at the same time, short circuits other than those which might be caused by fiashover at the contacts cannot develop, so. that a single source could be used, if desired, for supplying energy at both ends of the line circuit. In order to decrease the possibility of excess current flowing should flashover occur at the contacts of either relay ETR, and WTR, I have provided a resistor I92 in the line circuit. This resistor is of insufficient value to interfere with proper energization of relays ECTM and WCTM, but provides adequate protection against the possibility of an injurious short circuit.

It will be clear from the foregoing that by means of a novel and relatively simple line cir- ,cuit control arrangement, I have made provision for safe and effective control of highway crossing locations occurring within the single track stretch of my system.

In all of the track circuits which I have shown, with the exception of the highway crossing track circuits and the detector track circuits at track switch locations, I employ track relays (TR) having only a single contact finger which operates a repeater relay (TM) having the required number of contacts. The reason why I prefer to use a single point track relay is that this relay can be designed to have greater shunting sensitivity, thus permitting the operation of much longer track circuits than would be possible, for example, with a four point relay. It will be apparent, however, that where the track circuits'need not be of extreme length, the repeater relay of the track relaymay be dispensed with entirely, the track relay itself being equipped with the necessary number of contacts.

Lighting of the various signals in my system may be accomplished in the usual manner which is well known. It is intended, however, that the lever-controlled headblock signals at the ends of the sidings will be normally lighted, whereas. the automatic intermediatesignals will be normally dark but will become illuminated, when an entrance signal is cleared or a train is approaching the intermediate signal location.

In describing the operation of the cut section apparatus at locationF of Fig. la, a front contact coding cut section was used. B thi is meant that repeating of the code around the cut section is accomplished over one or more front contacts. This type of cut section is satisfactory where the code received by a track relay is directly repeated into another track circuit and the total length of the track circuits which are so controlled, including the first one, is not execssive. gization resulting from variation in track ballast resistance may be considerable in long track circuits, so that the time during which a front contact .of; a track relay is closed on code will al preciably increase when the relay isoverenergized, resulting in distortion of the repeatedcode. This distortion may be cumulative when the code is repeated over several cut sections by front contact coding, and may under certain conditions exceed the limits for proper operation of the decoding equipment.

To avoid this diimculty, a back contact coding cut section such as I have shown in. Fig. may be. used. This typeof cutsectio-n has a corrective characteristic, in. that it repeats short on periods as long 0 periods, andshort o periods as long "on. periods. Accordingly, the distortion of code received, by the, first track section will be compensated. for, or largely corrected, by the use of the back contact. coding cut section apparatus. The operation of this apparatus will be clear from the drawings so, that only a brief explanation of the repeating circuits will be given. It will be noted that I have provided each track relay with an FSA relay which is energized when its track relay is operated either by steady energy or by code, and with a BSA relay which is operated only when the track relay is following code. In this manner, selective control is provided, depending upon whether steady energy or coded energy is to be repeated over the cut section. When relay ETR is steadily energized, for example, a steady energy circuit for relay WCTM is closed over the back contact I95 of relay ETBSA and the front contact I96 of relay ETFSA. When relay ETR follows code, the code repeating circuit for relay WCTM includes the back point of contact I9'I of relay However, the variation in track relay enerparatus of Fig- 1a.

22 ETR, front contacts I98 and I99 of relays ETBSA and ETFSA, respectively, and back contact 200 of relay WTFSA. Corresponding circuits are effective for operating relay ECTM on steady energy or code, according as relay WTR is steadily energized or is following track circuit code.

Referring next to Fig. is which shows a modifled form of the trafiic direction control and traffic locking apparatus of Fig. la, the apparatus of this figure is quite similar'to that shown in Fig. 1a, the chief difference residing in the manner in which the polar stick relay 8LPR is controlled, as well as the manner in which this relay controls the selective energization of the traffic direction control relays at the two ends of the stretch. With trafiic assumed westbound and steady energy being received at the exit end (stretch unoccupied and both opposing headblock signals at stop), the westbound trafiice' relay BWFK will be energized so that its front contact 2M is closed. Since the traflic lever 8 occupies its normal position (traflic westbound), its contact 8W is closed so that polar relay SLPR is energized in the normal direction and contact IIII occupies its right-hand position, as shown. Accordingly, the circuit for energizing terminal IE2 is effective as soon as the starting button on lever B is depressed (so that relays 234ST and 234s are picked up). As pointed out herein-before, energization of terminal I02 is effective in energizing the westbound traffic direction con trol relay SWFSR.

A reversal of lever 8, closing contact 8E, will be effective for reversing relay BLPR since the left-hand winding .of this relay will receive energy over front contact ZBI of relay SWFK and contact SE of the lever. With relay BLPR reversed, an energizing circuit for terminal I I14 will be effective whenever the startin button is depressed, whereupon the eastbound trafiic direction control relay 8EFSR will be energized to effect the traiiic direction reversal in the manner previously explained. The apparatus of Fig. 16 also employs a polar stick trailic indication relay 815K controlled to one or the other position over a front contact 262 or 203 of the associated relay BWFK or 8EFK. Polar contact 204 of relay SFK controls the westbound and eastbound trailic indication.

One operating difference between the apparatus of Fig. le and Fig. 1a is that in the latter, the energizing circuit for one or the other winding of relay SLPR is checked over a contact (I68) of its corresponding indicating relay only, but not over both indicating relays, a in Fig, 1e. Accordingly, in Fig. la, a reversal of relay SLPR cannot be obtained unless the steady energy is received at the end of the stretch corresponding with the established traiiic direction. Also, in Fig. la, the initial energizing circuit for terminal I02 or IM includes a front contact (I 32 or I2!) of the corresponding indication relay. Thus, neither traffic direction control relay can be energized from the office unless an indication is re ceived, and this indication must correspond with the established trailic direction. It will be clear, therefore, that the apparatus of Fig. 1e will operate satisfactorily, but that additional refinements and checks have been introduced into the apparatus of Fig. la.

Fig, 1 shows a further modification of the en'- The apparatus of Fig. if eliminates the polar stick relay SFK of Fig. 1e, but is in other respects quite similar to the latter figure in is operation. That is to say, relay 

